“There is some information that they may have been intent to come to New York but not to continue what they were doing,” said Mr. Kelly, attributing the information to interrogations of Dzhokhar Tsarnaev. “The information that we received is something about a party — having a party,” he added. “Something to the effect of coming to party in New York.”

Mr. Kelly also confirmed that the carjacking victim who encountered the brothers on Thursday night said the suspects “were speaking in either Chechen or Russian, a language the driver didn’t understand. But he thought he heard the word ‘Manhattan’ in their conversation.”

The driver, who hasn’t been identified, eventually escaped from the brothers after letting them use his bank card to withdraw money from an automated-teller machine, authorities said. The older brother, Tamerlan Tsarnaev, 26, was killed in a firefight with police following the alleged carjacking episode, four days after the bombings.

While the brothers didn’t appear to have any intimate connection to New York City, Mr. Kelly said investigators in Boston and New York are looking into at least one visit by Dzhokhar Tsarnaev to New York last November.

Mr. Kelly said there may have been subsequent visits as well, and investigators have tracked other potential links to the New York City area. When the FBI was still hunting for the suspects, a friend of Dzhokhar Tsarnaev’s said FBI agents visited her mother’s house in Long Island, thinking he might try to see her there.

In one visit by the younger brother, he was photographed with four others in Times Square and posted the image on his Twitter account. Mr. Kelly said it wasn’t yet clear when the photo was taken and who else is shown.

“We’re trying to determine where they were” and what the purpose of the visits were, Mr. Kelly said.